//将两个有序链表合并为一个新的有序链表并返回。新链表是通过拼接给定的两个链表的所有节点组成的。 
//
// 示例： 
//
// 输入：1->2->4, 1->3->4
//输出：1->1->2->3->4->4
// 
// Related Topics 链表

package leetcode.editor.cn;

import static org.junit.Assert.assertEquals;

public class MergeTwoSortedLists {
    public static void main(String[] args) {
        Solution solution = new MergeTwoSortedLists().new Solution();
        ListNode l1 = new ListNode(1);
        l1.next = new ListNode(2);
        l1.next.next = new ListNode(4);
        ListNode l2 = new ListNode(1);
        l2.next = new ListNode(3);
        l2.next.next = new ListNode(4);
        ListNode result = solution.mergeTwoLists(l1, l2);
        assertEquals(result.val, 1);
        assertEquals(result.next.val, 1);
        assertEquals(result.next.next.val, 2);
        assertEquals(result.next.next.next.next.next.val, 4);
    }

    static class ListNode {
        int val;
        ListNode next;

        ListNode(int x) {
            val = x;
        }
    }

//leetcode submit region begin(Prohibit modification and deletion)

    /**
     * Definition for singly-linked list.
     * public class ListNode {
     * int val;
     * ListNode next;
     * ListNode(int x) { val = x; }
     * }
     */
    class Solution {
        public ListNode mergeTwoLists(ListNode l1, ListNode l2) {
            if (l1 == null) {
                return l2;
            } else if (l2 == null) {
                return l1;
            } else if (l1.val < l2.val) {
                l1.next = mergeTwoLists(l1.next, l2);
                return l1;
            } else {
                l2.next = mergeTwoLists(l1, l2.next);
                return l2;
            }
        }
    }
//leetcode submit region end(Prohibit modification and deletion)

}